A conventional maintenance inspection for an electrophotographic printer has required maintenance personnel to use a manual operation and consider each component to be normal if it is currently working, except for components that may be visually inspected such as toner in a transparent plastic vessel. The maintenance personnel have considered a component to be abnormal and exchange/repair it only when it is completely inoperable or very hard to operate. In other words, the conventional maintenance inspection has judged only whether a target component is normal or abnormal, and considered the component to be normal if judging it not to be abnormal.
The conventional maintenance inspection cannot avoid considering a component to be normal, but which may not completely be normal even thought it has not reached the apparently abnormal state (referred to as “deteriorated state” hereinafter). However, the subsequent continuous use of the deteriorated state is likely to bring about a near-future failure or very poor operation. Therefore, the conventional maintenance inspection often results in inoperativeness shortly after the maintenance inspection, annoying customers. In addition, it has been disadvantageously difficult for the conventional maintenance inspection to easily judge whether a component is in the deteriorated state.
The deterioration in a printer component may disable printing in the near future as well as gradually lower the print quality. A print operation depends upon components having various print functions as a whole. One deteriorated component may lower the entire print quality. However, the conventional maintenance inspection has difficulty in quantitatively evaluating the print quality. Even a detection of the image-quality deterioration cannot easily trace the causative component.
As described in further detail in U.S. Pat. No. 5,546,165, herein incorporated in its entirety by reference, scanners and desitometers have been used to measure density and process drive of the output prints in order to improve the system stability for electrophotographic systems over time. Corrective actions may be taken based on these measurements to maintain the system tone scale. However, the measurement of these two image quality attributes may not give an accurate indication of a system problem before image quality artifact levels are objectionable to end users.
As can be seen, there is a need for the improved measurement of image quality attributes in order to monitor image quality and make the appropriate adjustments before the artifact levels become objectionable. Moreover, there is a need for the improved measurement of image quality attributes to extend the perceived useful life of components of the system and, therefore, improve the perceived reliability of the printing system.